﻿Syntormon Loew (Diptera, Dolichopodidae) from Inner Mongolia, China, with the description of a new species

﻿Abstract Previously, no records of Syntormon Loew, 1857 species were known from Inner Mongolia (China). The genus is reported here from Inner Mongolia for the first time, with the description of a new species, S.sinicumsp. nov., along with two previously described species, S.dukha Hollis, 1964 and S.henanense Yang & Saigusa, 2000. Syntormonsinicumsp. nov. and S.dukha Hollis, 1964 are barcoded for the first time to support the species delimitation. A key to Syntormon species in China is provided.


Introduction
The genus Syntormon Loew contains more than 110 known species worldwide (Yang et al. 2006;Grichanov 2014;Grichanov 2021).Species of Syntormon can be recognized in both sexes by the antenna pedicel with one short finger-like projection projecting into the postpedicel.In recent years, Syntormon has been included in several molecular phylogenetic studies which have shed light on its phylogenetic position.Syntormon belongs to Sympycninae, within the Dolichopodidae sensu lato, and the intergeneric relationships within the Sympycninae have been demonstrated (Bernasconi et al. 2007;Lim et al. 2010;Germann et al. 2011).There have been 63 mitochondrial sequences from 10 species reported in these studies, of which 23 and 10 sequences were sequenced from Syntormon flexibile Becker, 1922 and S. pallipes Fabricius, 1794, respectively.These data have supported the molecular identification of S. pallipes and S. pseudospicatum (Chursina and Grichanov 2019;Tonguç et al. 2023).Still, most Syntormon species can only be identified by morphological characteristics (e.g.Drake 2020Drake , 2021)).
Thus far, 15 known species of Syntormon are known to occur China, with four species recorded in the Palaearctic realm, nine species recorded in the Oriental realm, and two species recorded in both realms (Yang et al. 2011) from forests, meadow steppe, steppe, desert steppe to Gobi Desert from northeast to southwest due to the greater precipitation in the northeast compared to the southwest and higher temperatures in the southwest compared to the northeast.However, there was no reports of Syntormon from Inner Mongolia.
The present study reports the distribution of Syntormon in Inner Mongolia for the first time, with records of a new species, Syntormon sinicum sp.nov., and two known species, S. dukha Hollis, 1964 andS. henanense Yang &Saigusa, 2000.This is also the first record of Sympycninae from Inner Mongolia.In addition, we provide the mitochondrial COI gene of S. sinicum sp.nov.and S. dukha Hollis, 1964 for the first time.A key to the species of the genus from China is provided.

Morphological taxonomy
The specimens on which this study is based were collected in Inner Mongolia during 2013-2021 by sweep net.Hohhot, Bayan Nur, Baotou, Xilingol League, Ulanqab, Chifeng, Tongliao, Hinggan League in Inner Mongolia were investigated, except for Hulun Buir.We focused on wet biotopes such as river basins, lakes, and forests for collection.All specimens are deposited in the China Agricultural University (CAU), Beijing and Entomological Museum of Institute of Grassland Research, Chinese Academy of Agricultural Sciences (IGRCAAS).Morphological terminology follows Cumming and Wood (2017).Keys by Yang et al. (2011) for Chinese species were used to identify specimens collected.The following abbreviations are used: acr = acrostichal, ad = anterodorsal, av = anteroventral, dc = dorsocentral, sc = scutellars, pd = posterodorsal, v = ventral, LI = fore leg, LII = mid leg, LIII = hind leg, CuAx ratio = length of dm-cu / length of distal portion of CuA.

DNA sequencing
Specimens used in this research were preserved in 95% ethanol at −20 °C.The mitochondrial genomic DNA was extracted from muscle tissue from thorax using the TIANamp Genomic DNA Kit (Tiangen) according to the manufacture's protocol.All PCR reactions were performed in a 50 μL volume: 2 μL DNA extract, 25 μL Taq PCR Master Mix, 2 μL of each primer, and 19 μL ddH 2 O.The reaction cycle was set as follows: 94 °C for 5 min of initial degeneration, 35 cycles for 94 °C for 30 s, 56 °C for 30 s, 72 °C for 1 min, and a final extension of 72 °C for 10 min.

Taxonomy Key to the species of Syntormon from China
Habitat.This species was collected in forests (Mount Jiufeng, Mount Helan, Xiaojinggou, Heilihe).
Thorax.Metallic green with pale gray pollinosity.Hairs and bristles on thorax black.5 acr bristyles uniserate; 6 dc bristles, long and strong; scutellum with 2 strong bristles and 2 much smaller bristles.Propleuron with yellowish hairs.
Abdomen.Metallic greenish with pale gray pollinosity.Hairs and bristles on abdomen mostly black, tergite 1 with yellow lateral hairs and bristles, hairs and bristles on tergites I-V yellow.Male genitalia (Fig. 2C): epandrium distinctly

Discussion
The study reports Syntormon from Inner Mongolia for the first time.Records of the genus in Inner Mongolia are shown in Fig. 4. The province has a temperate continental climate over more than one million square kilometers, with a variety of natural landscapes, including forests, meadows, and grasslands, which is suitable for Dolichopodidae.There are several reports of the genus from the neighbouring regions, such as S. flexibile Becker, 1922 from Hebei province and S. henanense Yang & Saigusa, 2000 and S. pallipes Fabricius, 1794 from Shaanxi province.In addition, S. beijingense Yang, 1998 andS. pallipes Fabricius, 1794 are recorded from Beijing and S. pallipes Fabricius, 1794 and S. xinjiangense Yang, 1999 are recorded from Xinjiang province (Yang et al. 2011).Furthermore, the previous insect investigations in Inner Mongolia mainly focused on Mount Helan (Alax League), Mount Jiufeng (Baotou), and Saihanwula (XilinGol League), and were limited in scope.Therefore, the species diversity of Sympycninae in Inner Mongolia is undoubtedly underestimated.
. The Palaearctic species are recorded from areas with a temperate continental climate, which is typical of Inner Mongolia, a province that belongs to Palaearctic China.The natural vegetation of Inner Mongolia encompasses a diverse range of ecosystems ZooKeys 1212: 143-152 (2024), DOI: 10.3897/zookeys.1212.119024Xingyang Qian et al.: Syntormon Loew from Inner Mongolia